Ondetti et al. in U.S. Pat. No. 4,105,776 disclose that various acylmercaptoalkanoyl and mercaptoalkanoyl derivatives of proline, hydroxy substituted proline, and alkyl substituted proline possess angiotensin converting enzyme inhibition activity and thus are useful as anti-hypertension agents.
Krapcho in U.S. Pat. No. 4,311,697 disclose that various acylmercaptoalkanoyl and mercaptoalkanoyl derivatives of diether or dithioether substituted prolines and ketal or thioketal substituted prolines also possess angiotensin converting enzyme inhibition activity.